2002 Fiscal Year Final Research Report Summary
In situ observation of phase transition in perovskite compounds by high-resolution synchrotron radiation powder diffractometry
| Project/Area Number |
13450267
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
YASHIMA Masatomo Tokyo Institute of Technology, Interdisciplinary Graduate School of Science and Engineering, Associate Professor, 大学院・総合理工学研究科, 助教授 (00239740)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Masahiko High Energy Accelerator Research Organization, Materials Structure Institute, Research Associate, 物質構造科学研究所, 助手 (60249901)
SASAKI Satoshi Tokyo Institute of Technology, Materials Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (10162364)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Synchrotron Radiation / Powder Diffraction / Rietveld Analysis / Phase Transition / Landau's theory / In Situ Observation at High Temperatures / High-Temperature Structure-Property Correlation / Electron Density Distribution |
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| Research Abstract |
La_<2/3>TiO_3-based provskite-stractured compounds are attractive materials for both wireless technologies and SOFC (Solid Oxide Fuel Cells) utilizing their excellent electrical properties. The electrical properties are strongly dependent on crystal structure of the perovskite solid solutions. The present letter reports the orthorhombic-tetragonal phase transition, remarking the precise unit-cell parameters that have not been determined in the literature, due to the lower angular resolution of the conventional laboratory-based diffractometer. This letter also demonstrates that the high-resolution synchrotron diffraction technique is very powerful to study the temperature dependence of the unit-cell parameters even near the transition point. This is worth publishing, because most of previous synchrotron diffraction works devoted to the compositional dependence.
We have investigated in situ a continuous transition between the orthorhombic and tetragonal phases in double-perovskite-structured La_<0.64>(Ti_<0.92>,Nb_<0.08>)O_3 by three X-ray powder diffractometers with different ~d/d resolutions of 0.03%, 0.06% and 0.10%. The d and ~d denote the λ/(2=sinθ ) and peak width where λ and θ are wavelength of X-ray and Bragg angle. Only the highest-resolution diffractometer of ~d/d =0.03% was able to detect the peaks splitting between 400 and 040 reflections, in the temperature range of 327βC to 339βC. It was found that the accuracy of the transition temperature is considerably improved with decreasing of ~d/d value. The maximum temperature where the peak splitting between 400 and 040 reflections is detectable increases, while the transition temperature determined by a power law decreases with decreasing of ~d/d value.
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[Publications] M.Yashima: "Photon Factory Activity Report 2001, Part A Highlights and Facility Reports"edited by K.Ito, R.Kato, K.Kojo, T.Kosuge, F.Mori, M.Nakatake, M.Nomura, T.Obina, K.Ohsumi, H.Sawa, M.Tanaka, N.Tomita, N.Usami, High Energy Accelerator Research Organization(KEK), Tsukuba, Japan. 3 (2003)
Description
「研究成果報告書概要(和文)」より
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